Four hundred or more participants needed for stable contingency table estimates of clinical prediction rule performance

An evaluation of the differences in paediatric skeletal trauma between fatal simple short falls and physical abuse blunt impact loads: An international multicentre pilot study

In cases where a deceased child exhibits trauma as a result of a physical abuse blunt impact load, a parent/caregiver may provide a simple short fall (SSF) as the justification for that trauma. The skeletal fractures remain difficult to differentiate between a SSF and physical abuse however, as both are the result of a blunt impact load, and are therefore biomechanically alike, and the rare nature of these fatalities means only anecdotal research has been available to validate such claims. The aim of this pilot study was to investigate if there may be differences in the skeletal fracture patterns and types resulting from SSFs compared with those resulting from physical abuse blunt impacts. Paediatric (<10 years) cases of fatal SSFs (≤1.5 m) and physical abuse were collected from the Victorian Institute of Forensic Medicine (Australia), Institut Médico-Légal de Paris (France), University of Pretoria (South Africa) and Great Ormond Street Hospital (England). For each case the intrinsic and extrinsic variables were recorded from medico-legal reports and skeletal trauma was documented using post-mortem computed tomography scans and/or skeletal surveys. Three SSFs and 18 physical abuse cases were identified. Of the SSF cases, two exhibited fractures; both of which were simple linear neurocranial fractures. Comparatively, 12 of the physical abuse cases exhibited fractures and these were distributed across the skeleton; 58% located only in the skull, 17% only in the post-cranial and 25% located in both. Skull fracture types were single linear, multiple linear and comminuted. This pilot study suggests, anecdotally, there may be differences in the fracture patterns and types between blunt impact loads resulting from a SSF and physical abuse. This data will form the foundation of the Registry of Paediatric Fatal Fractures (RPFF) which, with further multicentre contributions, would allow this finding to be validated.

Broad External Validation and Update of a Prediction Model for Persistent Neck Pain After 12 Weeks

STUDY DESIGN

A prospective observational study.

OBJECTIVE

To externally validate the prediction model developed by Schellingerhout and colleagues predicting global perceived effect at 12 weeks in patients with neck pain and to update and internally validate the updated model.

SUMMARY OF BACKGROUND DATA

Only one prediction model for neck pain has undergone some external validation with good promise. However, the model needs testing in other populations before implementation in clinical practice.

METHODS

Patients with neck pain (n = 773) consulting Norwegian chiropractors were followed for 12 weeks. Parameters from the original prediction model were applied to this sample for external validation. Subsequently, two random samples were drawn from the full study sample. One sample (n = 436) was used to update the model; by recalibration, removing noninformative covariates, and adding new possible predictors. The updated model was tested in the other sample (n = 303) using stepwise logistic regression analysis. Main outcomes for performance of models were discrimination and calibration plots.

RESULTS

Three hundred seventy patients (47%) in the full study sample reported persistent pain at 12 weeks. The performance of the original model was poor, area under the receiver operating characteristics curve was 0.55 with a Confidence Interval of 0.51-0.59. The updated model included Radiating pain to shoulder and/or elbow, education level, physical activity, consultation-type (first- time, follow-up or maintenance consultation), expected course of neck pain, previous course of neck pain, number of pain sites, and the interaction term Physical activity##Number of pain sites. The area under the receiver operating characteristics curve was 0.65 with a 95% Confidence Interval of 0.58-0.71 for the updated model.

CONCLUSION

The predictive accuracy of the original model performed insufficiently in the sample of patients from Norwegian chiropractors and the model is therefore not recommended for that setting. Only one predictor from the original model was retained in the updated model, which demonstrated reasonable good performance predicting outcome at 12 weeks. Before considering clinical use, a new external validation is required.

LEVEL OF EVIDENCE

3.

Brief Psychological Screening Questions Can be Useful for Ruling Out Psychological Conditions in Patients With Chronic Pain

OBJECTIVES

Psychological symptoms are highly prevalent in chronic pain patients. Timely and accurate identification may enable individualized treatment and improve outcomes. The aims of this study were to (1) investigate the concurrent validity of brief psychological screening questions assessing anxiety, fear of movement, stress, pain catastrophization, and depression in chronic pain patients, and (2) to determine screening question cut-points at which the likely probability of having these psychological states was <10%.

MATERIALS AND METHODS

Responses to 1-item or 2-item screening questions within each of these 5 psychological constructs were compared with those of validated full-length questionnaires in 894 patients with diverse chronic pain conditions.

RESULTS

Compared with scores from full-length questionnaires, brief screening question scores had correlations between 0.54 and 0.66, and area under the curve between 0.79 and 0.83. At the dichotomized threshold scores that we chose, the posttest probability after a negative test result ranged from 6.5% to 8.6% for all these psychological constructs, except fear of movement. The pretest probability was so high (70%) for fear of movement that no threshold resulted in a posttest probability (negative test result) that was below 10%.

DISCUSSION

Use of these screening tests and scoring thresholds would have correctly identified that between 38.5% and 60.5% of the sample were unlikely to have these psychological states (true negatives), with a false-negative rate between 3.4% and 5.3%. This would allow clinicians to focus on whether there are other patient attributes in those patients requiring more thorough investigation using comprehensive validated questionnaires or structured clinical interviews.